Pressure compensated ionization chamber fire detector system



M. J. M GINN April 12, 1966 PRESSURE COMPENSATED IONIZATION CHAMBER FIRE DETECTOR SYSTEM Filed Feb; 18, 1963 4 Sheets-Sheet l FIG. 2

I NVEN TOR. MARTIN J. McGlNN TORNEYS.

M. J. M GINN April 12, 1966 PRESSURE COMPENSATED IONIZATION CHAMBER FIRE DETECTOR SYSTEM 4 Sheets-Sheet 2 Filed Feb. 18, 1963 FIG. 4

INVENTOR.

MARTIN J, MCGINN @d/la7 w ATTORNEYS.

April 12, 1966 M. J. M GINN 3,246,312

PRESSURE COMPENSATED IONIZATION CHAMBER FIRE DETECTOR SYSTEM Filed Feb. 18, 1963 4 Sheets-Sheet 5 FIG 50 INVENTOR. MARTIN J. McGINN BY )(Qd/wy q )d/vy ATTORNEY April 12, 1966 M. J. M GINN 3,

PRESSURE COMPENSATED IONIZATION CHAMBER FIRE DETECTOR SYSTEM Filed Feb. 18, 1963 4 Sheets-Sheet 4 INVENTOR. MARTIN J. McGlNN v @1147 A TTORNEY United States Patent 3,246,312 PRESSURE COMPENSATED IONIZATION CHAMBER FIRE DETECTOR SYSTEM Martin J. McGinn, Blackhawk Trail, Oregon, Ill. Filed Feb. 18, 1963, Ser. No. 259,270 8 Claims. (Cl. 340-237) This invention relates to apparatus responsive to changes in the composition of a gas and more particularly to an electronic fire detector unit of the ionization chamber type for testing air for the presence of smoke or other combustion products.

My invention set forth in this application is an improvement of the invention set forth in copending application Serial No. 129,187, filed August 3, 1961, by Robert E. Bressler, now Patent No. 3,078,450, issued February 19, 1963, of which applicant is the owner by assignment.

Ionization type detectors, such as set forth in US. Patent 3,078,450, for detecting the presence of smoke and combustion products have the advantage that they detect the presence of combustion during its earliest stages or during what is known as the incipient period when combustion gases alone are being produced by the combustion. On the other hand, fire detection devices of the thermostatic or photoelectric type only respond to the later stages of the combustion when the fire has become well established. It is obvious, therefore, that a fire or combustion detection device which operates upon the ionization principle is much more effective in providing an early warning of the presence of combustion than detection devices of other types.

In the ionization chamber fire detector set forth in Patent 3,078,450, a flexible wall portion is utilized for balancing the pressure within the reference chamber with the pressure in the air-testing chamber so that the pressure in both these ionization chambers is substantially the same at all times. With this arrangement the detector can be finely adjusted to a very sensitive detecting state, since as barometric pressure changes the pressure in both chambers automatically changes to the same extent, thus eliminating the need for reduction of sensitivity of the device to compensate for pressure changes as required in other prior art ionization chamber type fire detectors. Due to their design, ionization chamber type fire detectors are operated from a source of DC power, and in the past such detectors have been designed only for operation in larger systems where a central DC power source is provided for supplying all of the individual detector units throughout the system.

It is, therefore, the main object of the present invention to provide an ionization chamber fire detector unit which contains its own DC. power supply and which can be connected to any convenient source of existing A.C. power,

Another object of the invention is to provide a construction of pressure compensated ionization chamber fire detector unit which is adapted for use in the home, small stores and business offices without the need of costly installation. In the past high quality, efficient, electronic fire detector systems of this type have only been available in large system layouts, such as required in institutions and in municipal or industrial applications. The unit of the present invention is the first to provide for use of ionization chamber type fire detectors as single units at selected locations with relatively simple installation.

It is another object of the invention to provide a construction of ionization chamber fire detector which can be installed and which can operate as independent units in a home, or the like, to give local fire alarm protection in selected areas or rooms.

Another object of the invention is to provide a construction of ionization chamber fire detector unit which can be wired directly into existing volt A.C. ceiling outlets.

Still another object of the invention is to provide a construction of ionization chamber fire detector which is relatively economical in cost and which can be installed by the individual homeowner.

A further object of the invention is to provide an ionization chamber fire detector unit which is relatively compact, pleasing in appearance, and which provides means for confirming operation of the device at a glance.

Still a further object of the invention is to provide a fire detector unit in which all circuits are deenergized through novel means for safety purposes when the cover is removed.

Still a further object of the invention is to provide a construction of ionization chamber fire detector unit having a simplified sensitivity adjustment for adjusting a unit to the individual locale.

Other and further objects of the invention reside in the simplified construction of the ionization chambers in the fire detector and the provision for attaching additional alarms, or the like, to the unit as set forth more fully in the specification hereinafter following by reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of the unitized fire detector assembly of the invention;

FIG. 2 is an enlarged vertical section view through the assembly of FIG. 1;

FIG. 3 is a bottom plan view of the fire detector assembly, on a scale somewhat reduced from that of FIG.

2; and particularly showing the arrangement of the power supply circuit components with the baseplate cover removed;

FIG. 4 is an electrical schematic diagram of the power supply and ionization chamber unit circuits;

FIG. 5 is a partial vertical section view similar to FIG.' 2'showing a modified form of the invention, and more particularly showing an improved construction of the ionization chamber unit;

FIG, 5a is a partial horizontal section view taken sub stantially along line 5a-5a of FIGS;

FIG. 6 is a vertical section view similar to FIG. 5, with parts omitted, showing a more simplified form of the ionization chamber unit of FIG. 5;

FIG. 7 is a top plan view of the ionization chamber unit of FIG. 6; and

FIG. 8 is an electrical schematic diagram showing the electrical circuit of the unit of FIGS. 6 and 7.

All of the prior art ionization chamber type electronic fire detector systems normally employ a control panel which is designed and required for monitoring, regulating and controlling .a plurality of individual fire detector unit-s. Such systems normally cost in excess of $500.00 and due to economics are only employed in large installations, such as institutions and municipaland industrial applications where rigid code requirements must be met. The present invention now permits the same effective quality of control and regulation required of institutions for less than one-tenth of the above-mentioned system cost and allows the individual homeowner or purchaser to utilize the most exact, eflicient and capable type of fire detecting system within his own home or office at a cost easily within reach of his means.

Referring to the drawings in greater detail, wherein similar reference numerals are used to designate similar components, the unitized fire detector system of the in vention comprises a baseplate l', preferably circular in form and carrying the depending flange 2 about the perimeter thereof. The baseplate contains a central aperture 3 and is adapted for mounting directly -to a 110 volt A.C. ceiling outlet, with the electrical connections being made by wires passing through aperture 3. If at a particular locale .an A.C. outlet box is not available in the ceiling, the baseplate can be mounted flush on the ceiling with mounting screws, with an extension cord supplying conventional 110 Volt AC. power to the unit from an available wall outlet through the auxiliary line plug 4 to be explained more fully hereinafter.

The DC. power supply circuit shown in FIG. 4 is carried on a printed circuit board 5 or the like, which is connected by suitable means to bosses 6 extending from and integrally molded-in baseplate 1. Baseplate 1 is constructed of insulation material and preferably of a fire resistant plastic material. The various circuit components of the' power supply are carried by the underface of printed circuit board 5 about the perimeter area thereof independing relation as shown, with the printed circuit being carried on the upper surface of the board.

The D.Cl power supply circuit consists of AG. input conductors 7 and'8 which, by means of double-pole, double-throw switch 9, are connectable to conductors 10 and 11 for connecting the circuit to an AC. ceiling outlet through the baseplate aperture 3, or to auxiliary line plug 4, to which 110 Volt AC. power can be supplied by means of a conventional extension cord. The switch 9 may be of conventional form or a less expensive arrangement of selectively connectable plug jacks for completing the desired circuit. Adjacent the point at which AC. power is supplied to the circuit, conductors 7 and 8 are each interrupted by a pair of female plug jacks 12 and 13 with a cooperating pair of jumpered male jacks 14 and 15, carried by a mounting 16 on annular baseplate cover 17 for respectively completing and interrupting power supply lines 7 and 8 when cover 17 is connected to baseplate 1 by means of mounting screws 18 and when cover 17 is removed from' the baseplate, respectively.

When the cover is'iri position on the baseplate jacks 14 and are disposed in electrical contact with female plug jacks 12 and 13 and are removed therefrom to open the circuit whenever cover 17 is removed from the baseplate. Thus these jacks act as a four-prong safety interlocking circuit breaker to'remov'e power from all parts of the circuit whenever cover 17 isremove'd for purposes of maintenance, or the like. The interlocking safety switch may be molded directly into cover 17 and it will be noted that the central aperture of the cover is arranged so that cover 17 must be removed to break the electrical circuit before the ionization chamber unit, indicated generally at 19, or its associated outer cover 20, can be removed to completely eliminate any possibility of electric shock while working on any portion of the unit.

Inthe circuit; of FIG. 4, capacitor 21 is connected in series with diode rectifier 22, and capacitor 23 is connected in series withtlio'de rectifier 24 with these series circuits connected in parallel across input power conductors 7 and 8. Conductor 7 is connected to the parallel circuit at the junction of capacitors 21 and 23, and conductor 8 is connected through fuse 25 and dropping resistor 26 to the junction of oppositely connected diode rectifiers 22and 24. The unregulated output DC. voltage from this circuit is taken from terminals 27 and 28 at the junction of capacitor 23-diode 24 and capacitor 21- diode 22, respectively. Terminal 27 is connected through series resistor 29 to the anode of Voltage regulator tube 30, while terminal 28 is connected to the cathode of voltage regulator tube 31. The cathode of tube 30 and anode of tube 31 are connected in series to provide a circuit for regulating the D.C. output voltage between terminals 27 and 28. In one form of the invention, tube 30 may be an 0A2 glow-discharge tube and tube 31 may be an 0C2 glow-discharge tube of the type manufactured by Radio Corporation of America.

The regulated output supply voltage of approximately 220 volts D.C. is thus supplied at terminals 32 and 33, with the anode of tube 30 connected to terminal 32 through the series circuit of filter resistor 34, relay coil 35 and resistor 36, and the anode of tube 31 is connected to terminal 33 through the normally closed reset switch 37, of the push button type. The circuit is completed by filter capacitor 38 and resistor 39 connected in parallel across tubes 30 and 31, as shown.

An audio alarm buzzer 40 and a female volt plug 41 are connected in parallel across conductors 7 and 8 through a series circuit including fuse 43 and the normally open movable relay contactor 42, which is operable upon energization of relay coil 35. As shown in the various drawings, receptacles or plugs 4 and 41 and reset switch 37 are mounted on depending flange 2 for easy access and operation from outside the unit. Plug 41, which is energized upon the sounding of an alarm by the ionization unit 19, may be connected to other exterior alarm systems at remote locations or may be connected for performing various other functions upon the sounding of an alarm, such as to turn off fans and blowers, automatically close electrically-operated doors, activate a telephone alarm or an exterior flashing alarm light on the building or for operating a multitude of various other type devices. The audio alarm buzzer 40 mounted on the printed circuit board within the unit is provided with sufiicient volume to awaken and warn occupants of the protected premises of a pending danger from smoke or gases in the air.

The voltage power supply circuit is designed so that the 110 volt AC. input can vary as much as $30 volts without disturbing the regulated 220 volt DC. output at terminals 32 and 33 to the ionization unit 19. This circuit thus provides a safety feature far in excess of all area electrical line variances. The circuit has the additional feature that regulated voltage on the load is removed when either of the regulation tubes 30 or 31 is removed from its socket. The annular baseplate cover 17 is constructed of the same fire resistant plastic material as baseplate 1 and these members are preferably opaque. A transparent reflector 44 is connected in an aperture in cover 17 immediately adjacent glow-discharge tubes 30 and 31 so as to reflect light from these tubes, which normally glow when the circuit is operating to render an indication at a glance asto whether or not the unit is electrically connected and in functioning condition. If there is a malfunction in the power supply circuit, or if one of the tubes is burned out, no light will be observed through the reflector 44, thus warning the occupant of the premises that the system is not functioning.

That portion of the unitized fire detector assembly of the invention containing the ionization chambers, or that portion of the circuit which detects changes in the composition of the gas being tested to initiate the alarm, is indicated generally at 19. This unit, as shown in FIG. 2, is basically the same as that disclosed in Patent 3,078,450, and comprises a generally cylindrical inner housing 45 constructed of a suitable plastic or other insulated material, housing a reference chamber and a gaseous discharge control tube, as will be explained more fully hereinafter. Inner housing 45 is of hollow construction and includes an upper portion 46 of larger internal diameter and a lower portion 47 of smaller internal diameter. The upper portion terminates in an insulating base portion 48 including a plurality of male plug jacks 49, 50 and 51 which engage corresponding male jacks mounted on printed circuit board 5 and electrically connected to terminals 32 and 33' of the power supply circuit to thus, removably connect ionization chamber unit 19 to the printed circuit board and to effect. the various electrical connections from the power supply circuit. to the ionization chambers and its associated control tube as shown in the wiring diagram of FIG. 4.

The electrical conductive electrode member 52 is connected to hermetically seal the lower end-of housing por tion 47 and integrally carries an upstanding hollow cy-v lindrical electrode portion 53 extendingintelior of lower portion 47 and concentrically positioned therein. Electrode 52 bounds the lower end of the reference chamber, generally designated at,54, and the top-of the test chamber generally designated at 55,

The upper end of the reference chamber is sealed by flexible bellows 56, positioned in upper portion 46, with the open end of the bellows being sealed to shoulder 57 of the inner housing member. The bellows thus hermetically seals the reference chamber to prevent entrance of moisture and foreign matter therein and to continuously equalize the pressure and density of the gas in the reference chamber with the gas in the test chamber. Radioactive material 58 is positioned on the outer surface of electrode portion 53 in a band or in patches to cause ionization of the gas in the chamber to establish a current flow therethrough, as explained later.

A second cylindrical electrode 59, which is preferably formed of wire mesh material, is disposed in spaced coaxial position with electrode 53, to provide an annular space therebetween, and is fixed at its upper end to an annular flange which is secured to a shoulder within lower portion 47, as shown. A cold-cathod gaseous discharge control tube 60 is positioned within cylindrical electrode portion 53 such that electrode 53 serves to shield the tube from the radioactive material 58. This shielding is particularly important in the region of the control grid 61 of the tube. The tube 60 includes a control grid 61 which extends through the lower end of the glass envelope and is electrically connected to common electrode 52. The tube also includes anode 62 connected by a conductor to cylindrical electrode 59, and by a conductor 63 to male jack 49 which is connected to power supply line 32. Conductor 63 extends through shoulder 57 and is sealed therein to maintain the hermetical seal of reference chamber 54 and extends to plug 49 through the space between bellows 56 and the wall of upper housing portion 46 so that the Wiring is contained completely within housing 45.

The control tube also includes a cathode 64 which is directly connected to the negative terminal 33 of the power supply through a circuit including conductor 65 and jack 59, with conductor 65 extending through and sealed within shoulder 57 in the same manner as conductor 63. Condenser '66 is connected between grid 61 and cathode 65 to initiate the arc discharge across tube 60 when the potential of the grid becomes sufiiciently positive to fire the tube.

Outer cover 20 of the ionization chamber unit 19 is connected to inner housing 45 by epoxy adhesive or by bonding the members together by spinning, since this cover is constructed of fire-resistant plastic material. Outer cover 20 extends through a central opening from baseplate cover 17 when the fire detector unit is completely assembled and the upper portion of cover 20' is constructed as shown, such that baseplate cover 17 must be removed from the assembly before the ionization chamber unit 19 and its associated cover 20' can be unplugged from the printed circuit board 5 and removed for test purposes or the like. The cover member is provided with an electrically conductive coating 67 which may be brushed, sprayed, evaporated, etc., on the inner surface thereof with the upper portion making electrical contact with a conductor 68 connected through one of the male plug jacks to the negative terminal 33 of the power supply circuit. Conductive coating 67 comprises one of the electrodes defining the test chamber 55 with the other boundary of the test chamber being defined by common electrode 52. As shown, the lower end of cover 20* is plurality louvered around the perimeter to allow the air or gas, which is being monitored for changes, to freely circulate through the test chamber 55 intermediate electrodes 67 and 52. With this construction, the test chamber 55 is positioned below basep-late cover 17 so that it is in a free circulation path with the air or gas being monitored.

A metallic shield member 69, having a threaded bore, is connected to the lower wall of cover 20 such that a flange thereof is in electrical contact with the electrically conductive coating 67, and thus in the electrical circuit 6. with terminal 33 of the power supply circuit. The outer portion of the shield member 69 is covered with a plastic sleeve 70, and a threaded lug 71 is connected in the threaded bore of shield member 69 for axial displacement therein by a plastic adjusting knob 72 carried on the lower end thereof. A band of radioactive material 73- is carried on the upper terminating end of lug 71, and by rot-ation of knob 72 it can be retracted into and extended from shield member 69 to thus control the amount of radiation from the radioactive material and the degree of ionization of the gas in the test chamber.

When combustion products are not present in the test chamber the distribution of voltages, across the series connected test and reference chambers and 54, is such that the potential of the control grid 61 connected to common electrode 52 is not sufficiently positive to permit firing of tube 60. In this state, a minute current in the neighborhood of three one billionth of an ampere flows across the chambers. When combustion products become present in test chamber 55 the impedance to flow of ionization current in the test chamber increases to cause a redistribution of voltage across the test and reference chambers so that the potential of control grid 61 becomes sufiiciently positive to trigger the firing of tube 60. Conduction of tube completes the output circuit of the power supply to an extent to cause energization of relay coil 35 in the anode circuit to thus close relay contact 42 placing buzzer 40 across the AC. line to sound an alarm and, additionally, energize other alarm devices which may be connected to .axuiliary plug 41. During normal operation of the device, when no combustion gases are present the potential drop across the relay coil is not sufficient to energize the same. A more thorough explanation of the electrical circuit of the ionization chamber unit is set forth in Patent 3,078,450 and is incorporated herein by reference.

A suitable removable vent lug (not shown) is provided in the Wall of reference chamber 54- of the units of FIGS. 2, 5 and 6, at an appropriate place to allow the pressure and density within the chamber to be initially adjusted for a particular locale and then again hermetically sealed.

A modified form of the ionization chamber unit, according to one aspect of the invention, is shown in FIG. 5 wherein, for purposes of explanation, primed numerals .areused to designate components corresponding to those shown in the form of the invention of FIG. 2. The improved ionization chamber unit of FIG. 5 is much more compact in construction and can be plugged into the same baseplate and printed circuit board assembly as shown in FIGS. 1-4, without departing from the spirit of the invention. The more compact unit comprises a shorter cylindrical housing 45' carrying a flexible bellows 56' hermetically sealed to a shoulder 57' interior thereof to define the upper extremity of the hermetically sealed reference chamber 54. The lower position of housing 45' is sealed by common electrode member 52', of circular construction, having a rod-like electrode portion 53' connected centrally thereon and extending upwardly interior of the reference chamber and through a central aperture in second electrode plate 59' which is connected to the side walls of housing 45' and which is disposed in spaced relation with electrode portion 53'. As indicated, a source of radioactive material 58 is connected to the electrode portion 53 intermediate reference chamber electrodes 52' and 59'. A support member 74 of electrical insulation material, such as plastic, is connected within the bellows above second electrode plate 59, as shown, and serves as a support for the tube 60" and capacitor 66'. Electrode 59 also serves to shield the tube from the radioactive material 58'. Tube 60' is a small three-electrode neon glow tube which operates in the same manner as tube in FIG. 4 and which is connected into the electrical circuit of the ionization chamber unit in an identical manner. The electrical circuit connections for the improved compact head of FIG. 5 will there fore not be explained in detail since they are identical with that shown in the diagram of FIG. 4. As before, the lead-in conductors 63 and 65' extend through and are sealed in the shoulder 57' and extend between the housing and bellows into electrical contact with the ap propriate jacks for connecting them to corresponding terminals 62 and 33, respectively. It should be understood that jacks 51 and 50 in the forms of the invention shown in FIGS. 2, and 6, are commonly connected to terminal 33 of the power supply, either by jumpers between these jacks on the ionization chamber unit and/or jumpers between corresponding female jack connectors commonly connected to terminal 33.

The tube 69 is preferably encased within a plastic coating of electrical insulation material, such as Silastic, to prevent leakage between the various electrode leads of the tube. Similarly, capacitor 66' can be commonly encased in such a plastic coating and since such a coating maintains these components completely isolated and impervious to changes in atmospheric conditions, the encased tube and capacitor can be mounted outside the reference chamber if such is more convenient for a more particular application. Encapsuling these components in this manner maintains them in the same state as if they were encased within the reference chamber itself.

The insulating base portion 48 carries a depending outer channel portion 75 about the periphery thereof forreceiving and retaining the plastic outer cover 20' which is provided with an electrically conductive coating 67 in the same manner as outer cover 20. The cover is provided with a shoulder portion 76 for engaging baseplate cover 17 to prevent removal of the ionization chamber unit before cover 17 is removed to break all of the electrical circuits through the safety line-breaking device carried by mounting 16. Cover 20' is louvered, as shown, at its lower end to allow gas being monitored to freely circulate through the test chamber 55' with the coating 67' which forms one electrode of the test chamber being electrically connected to terminal 33 of the power supply through spring connector 68 disposed in frictional contact therewith. The test chamber radioactive material 73 is mounted in the same manner as shown in FIG. 2 with the sensitivity of the ionization chamber unit being adjustable by axially displacing the radioactive material relative to the metallic shield member 69. It can thus be seen that while the improved construction of FIG. 5 operates in the same manner as the device shown in FIG. 2, the structure is considerably simplified and more compact. The improved design also lends itself to simpler manufacturing techniques.

A more simplified construction of the ionization chamber unit of FIG. 5 is shown in FIG. 6, where, in lieu of mounting the radioactive material 73 on an adjustable member on the cover 20', the radioactive material is mounted below common electrode 52' on an extended portion 77 of the rod-like electrode portion 53' which extends through electrode 52' in sealed relation into the test chamber defined by electrode 52' and electrically conductive coating 67. With this arrangement the radiation from the radioactive material 73 in the test chamber cannot be varied for adjusting the sensitivity of the fire detector unit, so that sensitivity of the unit is adjusted by means of a potentiometer connected across the leads 63' and 65' which .are connected to terminals 32 and 33 of the power supply. The potentiometer, indicated generally at 78, is connected on a cap member 79 connected to housing 45 above the terminating end of the bellows enclosed therein. A series of resistors 80 are connected between conductors 63' and 65', as shown more particularly in FIGS. 7 and 8, with a plurality of electrical taps 81 provided intermediate adjacent resistors and on the ends of the series connected resistors. A movable contactor 82 pivoted at 83 is connected through conductor 84 to conductor 65' and terminal 33 of the power supply, through the connecting jack plug. With this arrangement a selected amount of resistance can be placed in parallel with the ionization chambers and the control tube with greater sensitivity of the device being provided when the largest amount of resistance is placed in parallel with the circuit. When contactor 82 is moved into engagement with the tap 81 connected directly with conductor 63 a shortcircuit is created across the ionization chamber unit, thus switching off all control from the unit. As shown, the movable contactor is disposed in the central position. The positioning of the potentiometer is normally performed at the factory but may be adjusted on location if a particular circumstance requires greater or lesser control'sensitivity from the fire detector. Also, after a unit has operated for a substantial length of time, and the tube has aged, to maintain sensitivity of the device at the same level it may be necessary to adjust the potentiometer 78. An electrical schematic diagram of the modified head construction of FIG. 6 is shown in FIG. 8. The bellows are subjected to changes in atmospheric pressures by air passages around the various wires which pass through apertures in the cap 79. Other than the sensitivity adjustment, operation of the device of FIGS. 6-8 is the same as the device shown in the other forms of the invention.

As previously stated, the reset switch 37 is mounted on depending flange 2 of the baseplate and is provided with a protruding head of the push-button type accessible from outside the unit as shown in FIGS. 1 and 3. The circuit and relay design is such that once the alarm circuit is completed it remains in that state until broken. Thus, after an alarm has been sounded the reset button 37 is pushed to break the circuit, after the air has cleared of smoke or the like so as to silence the buzzer and remote alarms and reset the circuit for operation.

The various plug-in ionization chamber units of FIGS. 2, 5 and 6 are all interchangeable in the basic unitized fire detector assembly since their electrical circuits are substantially the same although the construction of the various units is substantially different. As shown in FIG. 2, spring-type tube holders 85 are connected on the inner surface of cover 17 for engaging tubes 30 and 31 to hold the same in their sockets when the cover is mounted on the basep'late.

While the invention has been described in certain preferred embodiments it is realized that modifications may be made, and it is to be understood that no limitations upon the invention are intended other than those which may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is as follows:

11. A unitized fire detector assembly housing comprising, a base structure adapted for mounting on a ceiling, chambered detector means having a vented portion disposed in the circulation path of gas having an electrical circuit adapted to close upon change in the composition or" the gas, said chambered detector means removably connected to said base structure, a DC. power supply circuit mounted on said base structure adjacent said chambered detector means, an A.C. input circuit connected to energize said DC. power supply circuit, alarm actuating means connected to said base structure connecting said power supply circuit to the circuit of said chambered detector means where-by said alarm actuating means is energized upon closing of the circuit in said chambered detector means, a cover connected to said base structure and enclosing said DC. power supply circuit and said alarm actuating means, switch means operatively connected in said A.C. input circuit and connected to said cover whereby said A.C. input circuit is opened to remove all power from said fire detector assembly when said cover is removed from the said base structure, said cover having an opening therein, an outwardly extending flange on said chambered detector means between the ends thereof of a width greater than the opening in said cover and disposed in overlying abutment with the inner surface of said cover adjacent said opening, and the vented portion of said chambered detector means extending through said opening and below said cover in the circulation path of the gas being tested, whereby said cover must be removed from said base structure before said detector means can be removed from said base structure.

2. A unitized fire detector assembly housing as set forth in claim 1, in which said base structure is generally circular in shape and said chambered detector means is connected substantiallycentrally thereof and in depending relation thereto.

3. A fire detector assembly comprising, a baseplate adapted for mounting to a ceiling, a DC. power supply circuit having an output and an input circuit, means supporting said power supply circuit on said baseplate, alarm means connected to the means supporting the power supply circuit, a pair of ionization chambers having electrodes with said chambers connected in electrical series with each other and said alarm means and with this series circuit connected across the output of said power supply circuit, one of said chambers acting as a comparison chamber and the other of said chambers acting as a test chamber and open to the gas 'being tested, a discharge tu-be connected across said chambers and adapted to fire and energize said alarm means upon change in the composition of the gas in the test chamber, said pair of ionization chambers removably connected to said means supporting said power supply circuits, a cover member removably connected to said baseplate and enclosing said power supply circuit and said alarm means, switch means operatively connected in said input circuit and connected to said cover whereby said input circuit is opened to remove power from said fire detector assembly when said cover is removed from said baseplate, said cover having an opening therein, an outwardly extending flange on said pair of ionization chambers of a width greater than the opening in said cover and disposed in overlying relation with the inner surface of said cover adjacent said opening, and at least the open ionization chamber acting as a test chamber extending from said cover through the opening in a free circulation path of the gas being tested, whereby said cover must be removed from said baseplate before said pair of ionization chambers can be removed from said means supporting said power supply circuit.

4. A device for the determination of changes in the composition of a gas comprising, a base of insulating material having contact jacks connected therein, a sleeve of insulation material extending from said base, a metallic disc sealing the end of said sleeve remote from said base, a flexible bellows connected to the inner bore of said sleeve intermediate said base and said disc forming a comparison chamber intermediate said bellows and said disc, said comparison chamber being hermetically sealed and filled with gas, a second metallic disc connected in said comparison chamber intermediate said first disc and said bellows and having a central aperture therein, an electrically conductive rod connected to said first disc and extending axially of said comparison chamber through the aperture of said second disc and disposed in spaced relation with said second disc, a shelf of insulation material connected above said second disc, a glow tube having a cathode, anode, and control electrode supported on said shelf, said cathode electrically connected to one of said contact jacks and a capacitor supported on said shelf connecting said cathode to said rod, said anode electrically connected to another of said contact jacks and to said second metallic disc, said control electrode connected to said rod, a first radioactive substance connected to said rod intermediate said first and second metallic discs to ionize the gas in said comparison chamber, a conducting shield connected to said base and extending coaxially of said sleeve and enclosing the end thereof in spaced relation, said conducting shield electrically connected to said first contact jack and said shield and said first disc defining a test chamber, vent means in said shield to allow circulation of the gas to be tested through said test chamber, a second radioactive substance arranged in said test chamber and electrically connected to said conducting shield to ionize the gas in said chamber, whereby upon applying voltage to said contact jacks and upon a change of the composition of the gas in the test chamber said glow tube conducts to close a path across said contact jacks.

5. A device for the determination of changes in the composition of a gas as set forth in claim 4 in which said conducting shield is constructed of plastic material, and an electrically conductive coating deposited on the inner surface thereof.

6. A device for the determination of changes in the composition of a gas comprising, a base of insulating material having contact jacks connected therein, a sleeve of insulation material extending from said base, a metallic disc sealing the end of said sleeve remote from said base, a flexible bellows connected to the inner bore of said sleeve intermediate said base and said disc forming a comparison chamber intermediate said bellows and said disc, said comparison chamber being hermetically sealed and filled with gas, a second metallic disc connected in said comparison chamber intermediate said first disc and said bellows and having a central aperture therein, an electrically conductive rod connected to said first disc and extending axially of said comparison chamber through the aperture of said second disc and disposed in spaced relation with said second disc, a shelf of insulation material connected above said second disc, a glow tube having a cathode, anode, and control electrode sup ported on said shelf, said cathode electrically connected to one of said contact jacks and a capacitor supported on said shelf connecting said cathode to said rod, said anode electrically connected to another of said contact jacks and to said second metallic disc, said control electrode connected to said rod, a first radioactive substance connected to said rod intermediate said first and second metallic discs to ionize the gas in said comparison chamber, a conducting shield connected to said base and extending coaxially of said sleeve and enclosing the end thereof in spaced relation, said conducting shield electrically connected .to said first contact jack and said shield and said first disc defining a test chamber, vent means in said shield to allow circulation of the gas to be tested through said test chamber, a portion of said rod extending through said first disc into said test chamber, a second radioactive substance connected on said rod portion for ionizing the gas in said test chamber whereby upon applying voltage to said contact jacks and upon a change of the composition of the gas in the test chamber said glow tube conducts to close a path across said contact jacks.

7. A device for the determination of changes in the composition of gas as set forth in claim 6, including a cap closing the end of said sleeve adjacent said base, and potentiometer means connected on said cap and electrically connected across said contact jacks for varying the detecting sensitivity of the device.

8. A device for the determination of changes in the composition of .a gas as set forth in claim 7 in which said potentiometer means includes a plurality of resistors connected interior of said cap adjacent the end of said bellows.

References Cited by the Examiner UNITED STATES PATENTS 2,597,310 5/1952 Fisher 321-15 X 2,724,823 11/1955 Toepfer 340--283 3,078,450 2/1963 Bressler 340-237 NEIL C. READ, Primary Examiner. 

1. A UNITIZED FIRE DETECTOR ASSEMBLY HOUSING COMPRISING, A BASE STRUCTURE ADAPTED FOR MOUNTING ON A CEILING, CHAMBERED DETECTOR MEANS HAVING A VENTED PORTION DISPOSED IN THE CIRCULATION PATH OF GAS HAVING AN ELECTRICAL CIRCUIT ADAPTED TO CLOSE UPON CHANGE IN THE COMPOSITION OF THE GAS, SAID CHAMBERED DETECTOR MEANS REMOVABLY CONNECTED TO SAID BASE STRUCTURE, A D.C. POWER SUPPLY CIRCUIT MOUNTED ON SAID BASE STRUCUTRE ADJACENT SAID CHAMBERED DETECTOR MEANS, AN A.C. INPUT CIRCUIT CONNECTED TO ENERGIZE SAID D.C. POWER SUPPLY CIRCUIT, ALARM ACTUATING MEANS CONNECTED TO SAID BASE STRUCTURE CONNECTING SAID POWER SUPPLY CIRCUIT TO THE CIRCUIT OF SAID CHAMBERED DETECTOR MEANS WHEREBY SAID ALARM ACTUATING MEANS IS ENERGIZED UPON CLOSING OF THE CIRCUIT IN SAID CHAMBERED DETECTOR MEANS, A COVER CONNECTED TO SAID BASE STRUCTURE AND ENCLOSING SAID D.C. POWER SUPPLY CIRCUIT AND SAID ALARM ACTUATING MEANS, SWITCH MEANS OPERATIVELY CONNECTED IN SAID A.C. INPUT CIRCUIT AND CONNECTED TO SAID COVER WHEREBY A.C. INPUT CIRCUIT IS OPENED TO REMOVE ALL POWER FROM SAID FIRE DETECTOR ASSEMBLY WHEN SAID COVER IS REMOVED FROM THE SAID BASE STRUCTURE, SAID COVER HAVING AN OPENING THEREIN, AN OUTWARDLY EXTENDING FLANGE ON SAID CHAMBERED DETECTOR MEANS BETWEEN THE ENDS THEREOF OF A WIDTH GREATER THAN THE OPENING IN SAID COVER AND DISPOSED IN OVERLYING ABUTMENT WITH THE INNER SURFACE OF SAID COVER ADJACENT SAID OPENING, AND THE VENTED PORTION OF SAID CHAMBERED DETECTOR MEANS EXTENDING THROUGH SAID OPENING AND BELOW SAID COVER IN THE CIRCULATION PATH OF THE GAS BEING TESTED, WHEREBY SAID COVER MUST BE REMOVED FROM SAID BASE STRUCTURE BEFORE SAID DETECTOR MEANS CAN BE REMOVED FROM SAID BASE STRUCTURE. 